CONSTRAINTS
A constraint is a condition that holds or must hold at a certain point in time. Two concrete subtypes of Constraint are covered by this notation: PreCondition and PostCondition. Constraint symbols are linked to the ActionKind symbols they relate to via generic links.
The symbol used to depict a constraint is a horizontal rectangle with two compartments, a small square one on one side and a long one on the other side. Line colour is dark grey and fill colour is light grey.
PreCondition
A precondition is a constraint that must be satisfied before an action of the associated kind can be performed.
The symbol used to depict a precondition is the abstract symbol for a constraint with the square compartment on the left-hand side, using an incoming arrow to depict entry.
PostCondition
A postcondition is a constraint that is guaranteed to be satisfied after an action of the associated kind is performed.
The symbol used to depict a precondition is the abstract symbol for a constraint with the square compartment on the right-hand side, using an outgoing arrow to depict exit.
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